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StcsArea
-
Return the CoordinateArea component when reading an STC-S document?
- Description:
- This is a boolean attribute which controls what is returned
by the
astRead
function when it is used to read from an StcsChan.
If StcsArea is set non-zero (the default), then a Region
representing the STC CoordinateArea will be returned by
astRead.
If StcsArea is set to zero, then the STC CoordinateArea
will not be returned.
- Type:
- Integer (boolean).
- Class Applicability:
-
StcsChan
-
All StcsChans have this attribute.
- Notes:
- Other attributes such as StcsCoords and StcsProps can be used to
specify other Objects to be returned by
astRead.
If more than one of these attributes is set non-zero, then the
actual Object returned by
astRead
will be a KeyMap, containing the requested Objects. In this
case, the Region representing the STC CoordinateArea will be
stored in the returned KeyMap using the key "AREA". If StcsArea
is the only attribute to be set non-zero, then the Object returned by
astRead
will be the CoordinateArea Region itself.
- The class of Region used to represent the CoordinateArea for each
STC-S sub-phrase is determined by the first word in the
sub-phrase (the "sub-phrase identifier"). The individual sub-phrase
Regions are combined into a single Prism, which is then simplified
using astSimplify
to form the returned region.
- Sub-phrases that represent a single value ( that is, have
identifiers "Time", "Position", "Spectral" or "Redshift" ) are
considered to be be part of the STC CoordinateArea component.
- The TimeFrame used to represent a time STC-S sub-phrase will have
its TimeOrigin attribute set to the sub-phrase start time. If no
start time is specified by the sub-phrase, then the stop time will be
used instead. If no stop time is specified by the sub-phrase, then
the single time value specified in the sub-phrase will be used
instead. Subsequently clearing the TimeOrigin attribute (or setting
its value to zero) will cause the TimeFrame to reprsent absolute times.
- The Epoch attribute for the returned Region is set in the same
way as the TimeOrigin attribute (see above).
Next: StcsCoords - Return the Coordinates component when reading an STC-S document?
Up: AST Attribute Descriptions
Previous: SpecVal - The spectral position at which flux values are measured
AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council